Stringed musical instruments are of ancient origin. During the succeeding centuries, many forms of such instruments have been developed. Many of these instrument forms are configured having a relatively narrow neck structure. That neck structure very commonly has an end at which the instrument strings are attached in such a manner as to permit adjusting of the tension thereof, and has another end affixed to a base of a body on which a bridge or saddle is provided to secure the opposite ends of these strings. The neck typically also has a structural portion having an exposed surface below the strings which is referred to as a fingerboard.
In the development of such instruments, fingerboards have resulted thereof that are either of the fretted type, or the fretless type, depending on the particular instrument in which it is located. A fretted fingerboard has a series of elongated narrow structures spaced apart from one another that project above a larger, major fingerboard surface. Each member of these series of structures have its long axis extending transversely across the major axis of the neck, and each is located at a precise location along the length of the fingerboard.
The purposes of these structures is to permit the musician using the instrument to shorten the effective length of the vibrating portion of a string positioned thereover. The musician is enabled to repeatedly select the effective lengths of the string at precise locations, each of which is determined using the fret chosen by the musician for this purpose, to thereby alter the pitch or frequency of the sound produced by the vibrating string. If the musician stops the string against the fingerboard major surface on the side of the fret opposite the bridge or saddle, the string will also be stopped against that fret and a precise vibration frequency in the string can thus be set determined by the distance of the fret from that bridge or saddle.
One can shorten the effective vibrating length of a string, causing it to vibrate at a higher frequency, by "stopping" it somewhere along its length--that is pressing it directly with a finger against the fingerboard as with violins, or pressing it against a fret with a finger as with guitars, or holding a slide or bottleneck against it. The term "stopping point" means the precise point at which the string contacts the fingerboard under pressure from the finger. With fretless instruments like violins, it is the musician's job to know the stopping point, i.e., how much to shorten the length of the string to get a desired pitch. With fretted instruments like most guitars, it is the maker's job to place the frets in the right locations along the neck. Thus, the string contacts the fret when the musician applies pressure to the string, and the contact between the fret and the string ensures a desired length of the string to produce a selected pitch.
With a fretless fingerboard, the stopping point is critical to musical performance and is determined solely by the musician. The resulting vibration of the length of the string between the stopping point and the bridge or saddle is determined by the precise position of the stopping point. Thus, there is no fret to predetermine the stopping point so as to provide a corresponding fixed frequency of vibration of the string. Instead, the musician must determine the stopping point by precise placement of the finger. Quite obviously, it is more difficult to play a fretless instrument than one having frets. With practice, the musician can memorize pitch locations on the fingerboard. The musician can even place visual pitch markers there, which is useful in realizing unusual tunings.
A fretless instrument, although more difficult to play provides advantages over a fretted instrument. A considerably wider range of frequencies for each string can be selected by a musician playing a fretless fingerboard than can be selected by a musician playing a fretted fingerboard. In the latter situation, the number of different frequencies available for a fretted instrument is, as a general matter, limited by the number of frets provided.
More specifically, the fretless fingerboard is not limited to a particular tonal scale, or the set of tones available for a string in a fretted fingerboard predetermined by the placement of frets along the fingerboard. In addition, certain playing techniques for varying pitch are desired to give unusual acoustical results, particularly in jazz and rock music. Also, in such music, other kinds of sounds are desired to be generated which result from "slapping" the strings with the thumb or "popping" the strings by pulling on them. A wider range of sounds from these methods will result when used on a fretless fingerboard differing from the sounds obtained using them on a fretted fingerboard as has been done traditionally.
To date, there have been a variety of materials used to construct stringed musical instruments. Such materials include composite materials used in the construction of the body, neck, fingerboard, and transducers, if the instrument is electrified. Examples include flakeboard laminates for tops and backs, plastic resin/fiberglass (both with and without further reinforcement with carbon fiber, aramid, and the like) solid and hollow bodies. Various materials have also been used for the necks including wood, fiberglass, carbon aramid, different metal alloys for truss rods, and plastic composites for fingerboard construction.
One problem associated with fretless fingerboards is premature wear of the playing surface. In various electrified instruments such as electric guitars, bass guitars, pedal steel guitars, lap steel guitars, and acoustic dobros, for example, nickel steel alloy strings are utilized. Such strings are exceedingly harder than the surface of the fingerboard, thus, leading to rapid premature wear of the surface. In fretted fingerboards, there is less concern for fingerboard wear, since the frets directly contact the strings. The frets are typically made of the same nickel steel alloy as the strings and better can resist the wear arising from contact with the metal strings. In acoustic instruments, strings with less hardness are used, but wear and abrasion to the fretless fingerboard, typically made of wood, still occurs.
In fretless stringed musical instruments, the musician's finger acts as a fret to shorten the effective vibrating length of the pressed string for tonal sound (i.e. determines the stopping point). Fingers are soft, and with direct contact they damp a string's vibration considerably. That is why most plucked string instruments have frets: the fret forms a hard well defined terminus to the string's vibrating length, so the finger does not touch the active part of the string. With more massive strings, the greater kinetic energy allows a more fuller tone in spite of the damping. One plucked fretless string instrument, for example, is the fretless bass guitar. Its notes are generally lower in frequency than encountered in a standard-tuning guitar. As a result, there is no significant problem with damping of the timbre by the fingers when the string is directly pressed against the fingerboard. Another way to improve the tonal qualities of a fretless stringed instrument is to have a fingerboard surface with a very low frictional resistance. This minimizes the damping effects of the fingered vibrating string.
To improve wear resistance and tonal qualities especially with heavier than usual gauge strings, several materials such as aluminum, steel, glass, and plastic have been used. Aluminum and steel fingerboards have been acceptable materials in terms of wear resistance and string tone, but with nickel strings, considerable wear still occurs. Glass fingerboards have good hardness and very low frictional resistance than metal surfaces for excellent tones, but glass is breakable and susceptible to scratches and abrasions. Plastic fingerboards provide acceptable tones but the wear and abrasion resistance is unacceptable.
For the foregoing reasons, there is a need for a stringed musical instrument having an improved fretless fingerboard that resists the wear and abrasion of metal strings better than prior fingerboards (fretted and fretless), enhances the tone quality, is more flexible to play, is simple to fabricate, and permits playing techniques not satisfactorily possible with fretted instruments.